From PathfinderWiki
The demonic rune of Cyth V'sug.

The island of Goroyasa sits off of the south-western corner of the Valashmai Jungle, as far away from the rest of Tian Xia and civilisation as it is possible to be. Like the rest of the Valashmai Jungle, Goroyasa is deeply hostile to outsiders but here it is because every single plant and animal shares a foul fungal infection that afflicts all life across the island. This fungal infection grants its bearers strange powers but, in exchange, saps them of their free will. The slaves of Goroyasa, as the human inhabitants of the island are known, are devout followers of Cyth-V'sug, demon lord of fungus and parasites, but how much influence Cyth-V'sug has over the island's fungal entities, or even if he is aware of its existence, is unknown.1